A heat sink includes a fin unit (10) and a heat pipe (40) for transferring heat from a heat-generating device to the fin unit. The fin unit includes a plurality of fins (20) parallel to each other. A flow channel (23) is defined between any of two neighboring fins for an airflow flowing therethrough. Each fin defines a through hole (25) having an axis of symmetry which extends along the flowing direction of the airflow. The through hole is for extension of the heat pipe therethrough. A plurality of protrusions (221, 222, 223, 224) extend outwardly from each fin. The protrusions being arranged irregularly around the heat pipe for guiding the airflow flowing to the heat pipe.